Theoretical study of the stability and electronic structure of Al(BH4)n=1→4 and Al(BF4)n=1→4 and their hyperhalogen behavior

Using density functional theory (DFT), we have systematically calculated the equilibrium geometries, electronic structure, and electron detachment energies of Al(BH(4))(n=1→4) and Al(BF(4))(n=1→4) at the B3LYP/6-311+G(2d,p) level of theory. The electron affinities of Al(BH(4))(n) not only exhibit odd-even alternation, just as seen in (BH(4))(n), but also, for n = 3 and 4, show a remarkable behavior: whereas the electron affinities of BH(3) and BH(4) are, respectively, 0.06 and 3.17 eV, those of Al(BH(4))(3) and Al(BH(4))(4) are 0.71 and 5.56 eV. Results where H is replaced by F are also very different. The electron affinities of BF(3) and BF(4) are, respectively, -0.44 and +6.86 eV, and those of Al(BF(4))(3) and Al(BF(4))(4) are 1.82 and 8.86 eV. The results demonstrate not only marked difference when H is replaced by F but also substantially enhanced electron affinities by almost 2 eV when BH(4) and BF(4) units are allowed decorate a metal atom, confirming the recently observed hyperhalogen behavior of superhalogen building blocks.     

A facile approach for morphosynthesis of Pd nanoelectrocatalysts

A facile approach has been developed for synthesis of highly-structured, anisotropic Pd nanostructures. The dendritic Pd nanostructures show superior performance toward oxidation of formic acid and methanol for fuel cell application.     

Effect of crystal potential on electric field gradient calculations due to impurities in cubic metals

The electric field gradients caused by interstitial and substitutional point defects in f.c.c. metals have been studied. The perturbation on the host electron distribution has been calculated self-consistently using density functional formalism. The effect of strain caused by size difference between host and impurity atoms is treated in the point-ion model. The influence of the host potential on impurity perturbation is incorporated within the spherical solid approximation. The theory is applied to positive muon and mono-vacancy in Al and Cu hosts. The theoretical results are in good agreement with experiment and illustrate the importance of both strain and conduction electron contribution to the electric field gradient.     

Rotational diffusion of dyes in micellar media from transient absorption

Solubilizer effects in dye solutions have been investigated by subnanosecond laser-pulse photometry. Different models for the transient dichroism of dye-micelle solutions are proposed. Computer fits of the experimental curves indicate that the model where dye molecules rotate within the liquid-like interior of the micelles is the most realistic one. Since the measured rotational diffusion times differ for different dyes in almost the same way as for pure highly-viscous solvents, the dye molecules do not act merely as labels for the rotation of the micelles, but rotate themselves considerably. It is shown that the rotational diffusion of dye molecules and micelles can be separated giving reasonable results for the size of the micelles. The results are compared with previous steady-state experiments.     

Rotational diffusion of dyes in solvents of low viscosity from transient-dichroism experiments

Rotational diffusion data from pulsed laser experiments are presented for dye molecules dissolved in alcohols and non-alcohols. Cresyl violet and fluorescein both exhibit strong dependence of the rotational motion upon solvent molecular structure. In complete contrast the rotational diffusion of the oblong dyes pyronine G and acridine orange do not reveal any specific solute-solvent interaction.     

Microwave Synthesis of Fused Pyrans by Humic Acid Supported Ionic Liquid Catalyst and Their Antimicrobial,Antioxidant, Toxicity Assessment,and Molecular Docking Studies

A series of fused quinolinyl and quinolonyl pyrans were synthesized via a one‐pot reaction of quinolinyl and quinolonyl carbaldehydes, malononitrile, and a 1,3‐diketone. The reactions were catalyzed by a new humic acid supported 1‐butyl‐3‐methyl imidazolium thiocyanate ionic liquid under microwave irradiation conditions. Antimicrobial, antioxidant, and toxicity studies displayed various biological activities depending on structure of the pyrans.     

Stable Tetra‐ and Penta‐Anions in the Gas Phase

The quest for stable gas‐phase anions in highly negative charge states has been a great challenge. While multiply charged anions are stabilized in solids and liquids by compensating cations and solvation cells, respectively, stable anions containing less than a hundred atoms in the gas phase and capable of carrying charge beyond ?3 is unknown. Here, we report the discovery of thermodynamically stable tetra‐ and penta‐anions, containing less than 50 and 80 atoms, respectively, in the gas phase. A universal model is developed that explains their stability in terms of the synergy between closed shell, high electron affinity, and size and predicts new highly‐charged anions by using the known charged clusters as building blocks. Synthesis of these species can open a new chapter in materials chemistry.     

Improved pulse schemes for separated local field spectroscopy for static and spinning samples

An improved pulse sequence for SLF experiments based on the magic sandwich (MS) scheme for homo-nuclear dipolar decoupling is proposed. The sequence incorporates a double MS, both on I and S spins and has been named as EXE-MS2. The proposed scheme which has a scaling factor of 1 is observed to be free from low intensity artifacts and provides better line-widths particularly for S spins labeled at multiple sites. The pulse sequence which has been applied on static oriented samples incorporates the EXE scheme where direct polarization of the S spin in the B(0) field is utilized in the place of polarization inversion and is observed to perform well without any loss of sensitivity while ensuring considerable reduction in rf power input into the sample. The EXE scheme has also been tested for solid samples under MAS.     

On evolution of non-linear waves in polytropic reacting gases

In this paper we have studied the behavior of wave motion as propagating wavelets and their culmination into shock waves in polytropic reacting gases with same \(\gamma \)-law. An expansion wave resulting from the action of receding piston has been considered and the solution to this problem has been obtained. The propagation of weak waves has been considered and the flow variables in the region bounded by the piston and the characteristic wave front have been found out. The expansive action of a receding piston undergoing an abrupt change in velocity has been discussed. Central expansion fan and shock fronts have been studied and the solutions up to first order in the physical plane have been obtained. The effects of reaction mechanism on the solutions have been analyzed in each case.